Polymer solutions, aqueous developable thick film compositions, processes of making and electrodes formed thereof

Abstract

The invention is directed to a process and more particularly, to utilizing polymer solutions to make thick film compositions. In one embodiment the process is directed to the formation of photoimageable thick film compositions for use in photo-patterning methods to make photoimageable electrodes in flat panel display applications, including plasma display panels (PDP). Polymer solutions are obtained by directly polymerizing desired monomers in a desired solvent to form a desired polymer, rather than by dissolving a pre-made polymer in a desired solvent. Other ingredients are added to the polymer solution to directly form thick film pastes, including photoimageable thick film pastes.

1. A method of forming a thick film composition comprising the steps:
 (a) providing ethylenically unsaturated monomers; 
 (b) providing a high boiling point organic solvent with a boiling point in the range of 160° C. to 300° C.; 
 (c) combining the monomers of (a) with the solvent of (b) to effect polymerization to directly form a copolymer in said solvent thereby forming a polymer solution comprising said copolymer wherein said polymer solution has a viscosity of greater than 5 Pascal seconds at 25° C.; 
 (d) providing one or more functional powders; 
 (e) providing one or more inorganic binders; 
 (f) combining the polymer solution of (c) with functional powders of (d) and the inorganic binder of (e) to form a thick film composition. 
 
     
     
       2. The method of  claim 1  further comprising:
 providing a photohardenable monomer; 
 providing a photoinitiation system; and 
 wherein said photohardenable monomer and said photoinitiation system are combined in step (f) with the polymer solution of (c), the functional powders of (d) and the inorganic binder of (e) to form a photoimageable thick film composition. 
 
     
     
       3. The method of  claim 1 , wherein said organic solvent comprising 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate. 
     
     
       4. The method of  claim 1 , wherein said polymer solution has a solids content in the range of 10 to 60 percent, based on weight of total polymer solution. 
     
     
       5. The method of  claim 1 , wherein said polymer solution has an acid number in the range of 20 mg KOH/g to 90 mg KOH/g, as measured in said polymer solution. 
     
     
       6. The method of  claim 1 , wherein said polymer solution has a viscosity in the range of 100 to 1,500 Pascal seconds at 25° C. at a shear rate of 4/s. 
     
     
       7. The method of  claim 6 , wherein said polymer solution has a viscosity in the range of 500 to 1,500 Pascal seconds at 25° C. at a shear rate of 4/s. 
     
     
       8. A thick film composition formed by the method of any one of  claims 1 ,  2  or  3 - 7 . 
     
     
       9. A sheet comprising the composition of  claim 8 , wherein the composition has been dried to remove the organic solvent.